This project will characterize the electrical properties of bullfrog sympathetic neurons, and the modulation of those properties by neurotransmitters. Whole-cell recording from dissociated sympathetic neurons will be used to investigate the voltage- dependent sodium, potassium, and calcium currents that are responsible for generation of the action potential and control of repetitive firing. In addition, the actions upon these voltage- dependent currents by slow synaptic potentials, muscarinic agonists, and neuropeptides will be examined, both on the dissociated cells and on neurons in the intact ganglion. Peptides of particular interest are the luteinizing hormone-releasing hormone of teleost fish, the likely transmitter for the late slow excitatory postsynaptic potential in the ganglion, and substance P. The experiments will use single or dual electrode voltage clamp with patch electrodes in the whole-cell configuration, or single electrode voltage clamp with intracellular microelectrodes. These approaches will increase our understanding of the fundamental mechanisms that generate the electrical activity of nerve cells, and of the ways in which neurotransmitters act to modify the electrical activity of nerve cells, and of the ways in which neurotransmitters act to modify the electrical behavior of neurons.